WO 2015/194255 discloses a storage facility (purge stocker (1)) that has a mechanism for cleaning the interior of a container with use of a purge gas such as an inert gas or clean dry air (the reference signs in parentheses in this description of background technology are the reference signs used in the prior art document). The purge stocker (1) is provided with a purge device (30) that cleans the interior of a container (F) with use of purge gas. The purge device (30) includes a plurality of loading portions (31), a plurality of supply pipes (33) that are connected to the loading portions (31), a main pipe (41) that is connected to the supply pipes (33), and a mass flow controller (43) that adjusts the flow rate of the purge gas in the main pipe (41) (see paragraph [0029], FIG. 1, etc.).
In a storage facility such as that described above, it is not necessarily the case that containers (F) are always loaded on all of the loading portions (31), and therefore the purge device (30) adjusts the flow rate of the purge gas according to the usage rate of the loading portions (31). The mass flow controller (43) adjusts the flow rate such that when the purge device (30) is to supply the purge gas to the containers (F) at a target supply flow rate (TF), the flow rate is the result of multiplying the number (N) of loaded containers (F) by the target supply flow rate (TF), that is to say TF×N (paragraphs [0034] to [0037]). In other words, the flow rate is adjusted so as to increase as the number of containers (F) that are purge gas supply destinations increases.
In the case where a container (F) is not loaded on a loading portion (31), purge gas leaks out of the supply pipe (33) in that loading portion (31). The mass flow controller (43) adjusts the flow rate (=TF×N) such that the flow rate increases as the number (N) of loaded containers (F) increases. However, in the case where a container (F) is not loaded, purge air is ejected from the supply pipe (33) without resistance from a container (F), and therefore there are cases where relatively more purge gas flows out of that supply pipe (33). As a result, it is conceivable that the flow rate of purge gas supplied to the containers (F) that are loaded on loading portions (31) will fall below the target supply flow rate, and that a sufficient amount of purge air will not supplied to the containers (F). For example, by providing on-off valves (39) in the supply pipes (33) as illustrated in the prior art document, it is possible to suppress the flow of purge air to unoccupied loading portions (31) (see paragraphs [0045] to [0046], FIG. 4, etc.). It should be noted that if an on-off valve (39) is provided in each of the supply pipes (33), the structure becomes complex, the device scale increases, and equipment cost tends to rise.